A variety of techniques for obtaining improved reducibility of a fluorescent image has been proposed for an image reading apparatus that reads out an image on a document so as to create document image data from it.
For example, Patent Literature 1 discloses an image reading apparatus configured as follows. The image reading apparatus includes a visible light source for mainly emitting visible light and an ultraviolet light source for emitting ultraviolet light, and reads out one set of image data from an image on a document by irradiating the document with the visible light only and another set of image data from the image on the document by irradiating the document with the ultraviolet light only. In the image reading apparatus, in a case where an operator selects a color check mode in a reading mode, two sets of the image data are displayed to the operator so that they can be visually compared with each other. Then, the operator performs a color adjustment process in accordance with the visual comparison of the two sets of the image data, so as to determine an adjustment value. The adjustment value is stored in a memory. Thereafter, there is performed, in accordance with the adjustment value, a process of image data that are read out from an image on a document by irradiating the document with the visible light only.
Patent Literature 2 discloses a technique in which (i) an image is outputted by an image output apparatus, in accordance with RGB color chart data, (ii) light reflected by the image is measured in light in an environment in which a document on which the image is formed would be actually observed, (iii) in accordance with the measurement, an output profile for use in a process of an image containing a fluorescent portion is created, and then, the output profile is stored in an image processing apparatus, and (iv) for image data that are read out from an image on a document, a color conversion process from a Lab signal to a RGB signal by use of the output profile is performed in the image processing apparatus, so that improved color reproducibility of the image containing the fluorescent portion is obtained.
Patent Literature 3 discloses a technique in which (i) image data are read out from an image on a document by irradiating the document with ultraviolet light, (ii) a fluorescent color region image in the image data is identified, (iii) for image data that are read out from the image on the document by irradiating the document with visible light only, a color compression process is performed by use of a color compression parameter which is switched between parameters in accordance with the identification of the fluorescent color region image.
Patent Literature 4 discloses a technique in which (i) image data are read out from an image on a document by irradiating the document with ultraviolet light, and a fluorescent color region in the image data is identified, and (ii) for image data that are read out from the image on the document by irradiating the document with visible light, a color conversion process is performed in which a region corresponding to the identified fluorescent color region is color converted by using a fluorescent color—close color conversion table being set in advance.